refactor

school/Test.java

@@ -0,0 +1,40 @@
+package school;
+
+import library.Administrator;
+
+public class Test {
+    public static void main(String[] args) {
+        ManagementSys sys = ManagementSys.getInstance();
+
+        Student std = new Student("John", 20, "S2201110101");
+        sys.addPerson(std);
+
+        Teacher tch = new Teacher("Tom", 30, "T2201110101");
+        sys.addPerson(tch);
+
+        Staff stf = new Staff("Jerry", 40, "S2201110101");
+        sys.addPerson(stf);
+
+        Administrator adm = new Administrator("Jack", 50, "A2201110101");
+        sys.addPerson(adm);
+
+        Manager mgr = Manager.getInstance("Marry", 60);
+        sys.addPerson(mgr);
+
+        for (Person person : sys.getPersons()) {
+            person.speak();
+        }
+
+        sys.removePerson(std);
+        System.out.println("After removing John");
+        for (Person person : sys.getPersons()) {
+            person.speak();
+        }
+
+        sys.updatePerson(0, new Teacher("Tom", 30, "T2201110102"));
+        System.out.println("After updating Tom");
+        for (Person person : sys.getPersons()) {
+            person.speak();
+        }
+    }
+}